Fetal activity has long been recognized as a good predictor of fetal well being as discussed in Fetal Movements In utero—A Review, Sadovsky, E., M.D., Isr. J. Obstet. Gynecol. 1992; 3:27-36. Fetal activity monitoring techniques run the gamut from an expectant mother's subjective assessment of fetal activity via fetal activity monitoring apparatus for monitoring her abdominal movements to in utero ultrasound based techniques for “looking inside” her uterus. Fetal activity monitoring apparatus is designed to monitor an expectant mother's abdominal movements within the range of 8-25 Hz which is the natural frequency signature of an expectant mother's abdomen. Such abdominal movements are assumed to be largely the result of fetal activity as opposed to uterine contractions, respiratory movements, maternal posture movements, and the like, and therefore the 8-25 Hz natural frequency signature of an expectant mother's abdomen is hereinafter coined as “natural fetal activity frequency signature”.
An exemplary fetal activity monitoring apparatus is described in an article entitled “Measurement of Fetal Movements by Moving-Coil Transducer” by Adler D., et al., IEEE Transactions on Biomedical Engineering, Vol. BME-27, No. 12, December 1980 which employs two moving-coil transducers placed on the left and the right sides of an expectant mother's abdomen to pick up abdominal movements. This apparatus requires an about 80 dB electrical signal amplification for fetal activity detection at least partially being necessitated to overcome the transducers' attenuation of frequencies in the natural fetal activity frequency signature, and offset the apparatus' high sensitivity to electromagnetic interference (EMI).